Health maintenance organizations have the mission, incentive, communication tools, and credibility with patients to reach out to teen members who use tobacco. The overall aim of this project is to refine and test both the potential reach and the efficacy of tobacco cessation support using a proactive telephone quitline combined with an interactive Web-based program for teens within a managed care environment. As part of a clinician-directed outreach effort, we will work closely with pediatric clinicians to maximize the program's reach into the teen smoker population as identified through the electronic data base of a large HMO. We will use letters and proactive outreach calls to assess current smoking status and recruit 600 15- to 18-year-old teen smokers who are interested in quitting and would be willing to receive cessation support via telephone and the Web. A second aim will be to randomly assign interested teen smokers to receive a proactive telephone- and Web-based tobacco cessation program or access to a website with cessation materials (control condition) to test the efficacy of the program on long-term cessation rates at 6- and 12-months. We will use several process measures to assess our ability to implement and consistently deliver both the telephone and Web components of the intervention. We will measure mediating variables to determine they support the hypothesized linkages between the theoretical constructs described by our cognitive behavioral model of action. An effective managed care partnership with clinicians to assess, recruit, and intervene with teen smokers would be of great interest to clinicians and health plan managers, highly exportable, and would be given high priority for implementation at the population level.